1 Then Joseph fell on his father’s face and wept over him, and kissed him.
2 And Joseph commanded his servants the physicians to embalm his father. So the physicians embalmed Israel.
3 Forty days were required for him, for such are the days required for those who are embalmed; and the Egyptians mourned for him seventy days.
4 Now when the days of his mourning were past, Joseph spoke to the household of Pharaoh, saying, “If now I have found favor in your eyes, please speak in the hearing of Pharaoh, saying,
5 ‘My father made me swear, saying, “Behold, I am dying; in my grave which I dug for myself in the land of Canaan, there you shall bury me.” Now therefore, please let me go up and bury my father, and I will come back.’ ”
6 And Pharaoh said, “Go up and bury your father, as he made you swear.”
7 So Joseph went up to bury his father; and with him went up all the servants of Pharaoh, the elders of his house, and all the elders of the land of Egypt,
8 as well as all the house of Joseph, his brothers, and his father’s house. Only their little ones, their flocks, and their herds they left in the land of Goshen.
9 And there went up with him both chariots and horsemen, and it was a very great gathering.
10 Then they came to the threshing floor of Atad, which is beyond the Jordan, and they mourned there with a great and very solemn lamentation. He observed seven days of mourning for his father.
11 And when the inhabitants of the land, the Canaanites, saw the mourning at the threshing floor of Atad, they said, “This is a deep mourning of the Egyptians.” Therefore its name was called Abel Mizraim, which is beyond the Jordan.
12 So his sons did for him just as he had commanded them.
13 For his sons carried him to the land of Canaan, and buried him in the cave of the field of Machpelah, before Mamre, which Abraham bought with the field from Ephron the Hittite as property for a burial place.
14 And after he had buried his father, Joseph returned to Egypt, he and his brothers and all who went up with him to bury his father.
As God had promised Jacob, Joseph “closed [Jacob’s] eyes in death” (Genesis 46:4), and Jacob died content (Genesis 45:28; 46:30). … It was customary in Egypt to embalm the dead, using an elaborate process of alteration and treatment of the body which ensured that its mummified remains would be preserved almost indefinitely. Joseph had his personal physicians undertake this process with his father’s body, a process which lasted forty days. It was also customary in Egypt to have approximately a seventy-day period of mourning, especially for a person of national importance. — Morris, pages 662-663
After the seventy-day period was over, Joseph and his brothers determined to set about obeying their father’s request that he be buried not in Egypt but in Canaan. … Joseph assured Pharaoh that the Israelites would all return after the burial was accomplished. … Pharaoh could see that the request was well intentioned and reasonable, especially in view of the oath [Joseph made to Jacob], and so readily granted permission. Evidently, he also gave orders that it should be recognized as an official Egyptian state funeral, with all due honors accorded to the dead.
The funeral procession consisted not only of Joseph and his brothers and their households (only the little ones remained behind in Goshen, as well as the flocks and herds—a fact which [likely] assured any Egyptians who might be skeptical that they would, indeed, return), but also the servants and elders of Pharaoh’s household, and all the elders of the land of Egypt. There were many cavalrymen for protection, as well as chariots (probably “wagons”) for transportation of food and supplies. — Morris, page 664.
The caravan seems to have stopped just east of the Jordan, at the site known as “the threshing floor of Atad,” Atad presumably being a man’s name. There the whole assemblage carried out a formal seven-day period of mourning. To all appearances it was an official Egyptian mourning ceremony, and was the object of much attention and discussion by the Canaanites of the area. The latter, in fact, gave the place the name Abel-mizraim (“Meadow of the Egyptians”) as a result. They may have wondered what a great body of Egyptians was doing there, instead of carrying out their funeral in Egypt; however, there is some evidence that Egypt actually controlled this region in those days.
When the mourning was done, Jacob’s sons took his body across the Jordan, into Canaan, and to the cave of Machpelah near Mamre. They they buried him, as he had commanded, giving testimony not only of love for their father but also of faith in God’s promises concerning the land, which someday would go to their seed for an everlasting possession. — Morris, page 665.
With Pharaoh’s assent, Joseph and his brothers then carry Jacob’s body to the land of Canaan and bury him in the cave of the field of Machpelah, where were buried Abraham and Sarah, Isaac and Rebekah, and Leah (Genesis 49:31)—this last of which, though unpreferred in her life (see Genesis 29:31) is thus granted enduring distinction in her death as the matriarchal representative of the third-interred “pair” in the Abrahamic line (Rachel was buried in the vicinity of Bethlehem; see Genesis 35:19). In Canaan Jacob’s family mourns him for a period of seven days, which, together with the similar reference in 1 Samuel 31:13, underlies the contemporary Jewish practice of shivah—i.e., setting aside seven days exclusively for the purpose of mourning over a deceased family member. — Wechsler, page 266.
Not only is Leah buried with Jacob in the grave of the patriarchs, but as Judah’s mother, she’s also in the line of the Messiah.